The Breeding Season and Ovulation Rate of DLS Ewes as Determined by Laparoscopy

Fahmy, M. H.; Dufour, J. J.

doi:10.4141/cjas86-031

Cited by 8 publications

(6 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It appears, therefore, that in the present study the ewes did not enter seasonal anoestrus after lambing in January-February. Differences between various years in the start and the end of the sexual season in the same breed have been reported for other breeds of sheep (Thimonier & Mauleon, 1969;Fahmi & Dufour, 1986).…”

Section: Discussionsupporting

confidence: 59%

The effect of a light pulse and melatonin, alone or in combination, on the reproductive performance of Finn-cross ewes in spring in Israel

1987

View full text Add to dashboard Cite

Adult Finn-cross ewes, pregnant from September matings, were kept under natural photoperiod (control, 30 animals) or with an additional exposure to a I h long. 300 lux light pulse, 16-17 h after an artificial dawn (light-pulse treatment, 32 ewes) for 2-5 months. After lambing, the supplementary light was discontinued and half of the ewes from each group were injected daily with 2 mg melatonin for an additional 2-5 months.The light-pulse ewes produced heavier lambs and more milk, as can be deduced from the higher rate of growth of their lambs during the first 10 days of life, than the control animals. The light-pulse and/or melatonin treatments delayed the occurrence of the first post-partum ovulation and oestrus (which occurred in the untreated animals about 4 and 6 weeks, respectively, after lambing), by 1-3 weeks. However, more ewes exhibited oestrus and cyclic activity in the light-treated than in the other groups. The fertility in the lighttreated group was, consequently, superior to that in the group kept under natural photoperiod, in spite of the similar lambing rate of the mated ewes of the different groups.It is concluded that the light-pulse, but not the melatonin treatment, had a beneficial effect on the reproductive performance of the ewes, as measured by the weight of the newborn lambs, the milk production of the dams during the first 10 days post-partum, and the cyclic activity of the ewes after February lambing in Israel.opened the way to the administration of exogenous TNTK.ODUCTION melatonin to induce the stimulatory effect of short days. In order to increase the reproductive efficiency of T h e exposure of ewes to increasing daylength is sheep it is necessary, among other ways, to increase apparently necessary before the stimulatory effect of the lambing frequency of the ewes, i.e., to obtain s h o r t d a y s ( E n g i i s h el aL i 9 8 6 ) Karsch el al. (1986), fertile matings during the anoestrous season. Since however, stated that the 'reproductive onset' in the the photoperiod was identified as the cue to the e w e s w a s l i n k e d t o cessa tion of the long day signal annual reproductive cycle of the animals (Marshall, a n d d i d n o t r e q u j r e exposure to short-day cues. In 1932), many attempts have been made to induce t h e pre sent study the possibility of inducing cyclic cyclic activity in ewes during the sexually quiescent activity in ewes after February lambings was period by exposing them to artificial light changes examined by exposing the animals to a light pulse which mimic those of the natural photoperiod a n d/or melatonin administration. In view of preprevailing before and during the breeding season v i o u s r e p o r t s o n t h e p o s s i b | e act ion of the photo-(review: Hansen, 1985). This strategy, however, p e r i o d t o w h i c h t h e d a m s a r e exposed before and necessitates light-proof buildings, which are imprac-a f t e r partU rition on their milk production and on the tical under field conditions. The existence of a g r o w t h of the litter (Pet...

show abstract

Section: Discussionsupporting

confidence: 59%

The effect of a light pulse and melatonin, alone or in combination, on the reproductive performance of Finn-cross ewes in spring in Israel

1987

View full text Add to dashboard Cite

show abstract

“…Ovulation without accompanying behavioral estrus is known to be relatively common in anestrous ewes (Fahmy and Dufour, 1986), and Wiggans et al (1970) reported two or more annual periods of estrous behavior in 35% of Rambouillet ewes that were observed daily for estrus for 4 yr. A reduction in "depth" of anestrus in less-seasonal breeds thus seems to be another explanation for the inconsistent cycles observed in our ewes. As ewes become less sensitive to inhibitory effects of long photoperiods, the anticipated distinct period of anestrus may be replaced with a less-distinct period of irregular cycles.…”

Section: Discussionmentioning

confidence: 99%

“…Blood samples were taken only from marked ewes to confirm that mounting was accompanied by ovulation. Silent ovulations, although they were expected to occur (Fahmy and Dufour, 1986), were not monitored.…”

Section: Methodsmentioning

confidence: 99%

Duration of the seasonal anestrus in sheep selected for fertility in a fall-lambing system.

Vincent

McQuown

Notter

2000

Journal of Animal Science

View full text Add to dashboard Cite

Crossbred ewes (1/2 Dorset, 1/4 Rambouillet, and 1/4 Finnsheep) from a flock being selected for spring fertility, defined as ability to lamb following ram exposure in May and June in Virginia (37 degrees N latitude), were used to study the duration of the seasonal anestrus. In the first 3 yr of the study (1992, 1993, and 1995), mature ewes were divergently selected based on EBV for fertility, and the duration of anestrus was measured by continuously exposing the ewes to vasectomized rams equipped with marking harnesses from mid-January until approximately August 1. Only ewes that had lambed in the previous fall were used to ensure that ewes were in a comparable physiological state, and the same rams remained with the ewes in each year to avoid induction of estrus by introduction of novel rams. The duration of anestrus in high-fertility ewes (n = 26; mean fertility EBV of 12.6%) was 28.4 d, which was significantly less than the 70.2 d of anestrus observed for low-fertility ewes (n = 15; mean fertility EBV of .3%). Five high-fertility ewes did not exhibit a period of anestrus. The regression of number of days of anestrus on fertility EBV was -2.15 +/- .72 d/%. In yr 4 (1997), 11 high-fertility and two low-fertility ewes were evaluated. None of these ewes exhibited a clear seasonal anestrus; six unequivocally cycled continuously. Between January 23 and July 31, the mean duration of anestrus for these ewes was only approximately 11 d. The duration of anestrus for high-fertility ewes seems to be the shortest reported for temperate sheep breeds.

show abstract

“…An experiment was conducted in early July when under the climatic conditions of southern Quebec (latitude 45°31', longitude 73°26'), the testes of rams are beginning to redevelop (1), and the ovaries of ewes are acyclic (9). Rams were given a series of LH (or vehicle) injections over a 6-day period.…”

Section: Experimental Animals and Planmentioning

confidence: 99%

Enhanced testosterone secretion in adult rams after establishment of a high-frequency, low-amplitude pattern of LH pulses in the nonbreeding season occurs without changes in the number or binding affinity of testicular LH receptors

Sanford

Baker²

1990

Acta Endocrinologica

View full text Add to dashboard Cite

When the LH signal in the ram is changed from one of large and infrequent pulses to one of small and frequent pulses, the testes quickly become more responsive to LH and testosterone secretion is elevated, perhaps because the number and (or) binding affinity of testicular LH receptors have increased. An experiment was undertaken in the nonbreeding season (July) with 10 adult Dorset \m=x\Leicester \m=x\Suffolk rams that were about 3.5 years of age and 69 \ m=+-\2 kg in body weight. Rams were given injections into the jugular vein of either 5 \g=m\g NIH\x=req-\ LH-S24 (in 1 ml saline) or vehicle every 80 min for 6 days. LH treament produced a series of LH pulses that occurred three times more frequently and were 70% less in amplitude than pulses in the control rams, without causing mean LH concentration to increase. Endogenously produced LH pulses were not evident in the treated rams after LH injection began. The modified LH-pulse pattern elevated mean testosterone concentration by 150% (assessed on days 2 and 5), and caused the cumulative testosterone response to LH pulses, estimated by multiplying testosterone-pulse amplitude by frequency per 6 h, to increase progressively by 180% (days \m=-\2 through 5). Enhanced testicular steroidogenic activity, presumably due to greater enzymatic activity and cholesterol availability within Leydig cells, was not associated with increases in either the concentration or affinity of LH\x=req-\ binding sites in the testis (assessed on days 3 and 6).The testes of adult rams secrete four to five times more testosterone in the breeding season than in the nonbreeding season (1, 2). Increased testos¬ terone secretion in the breeding season is the result of high-frequency, low-amplitude LH releases stimulating highly responsive testes (3). Increases in the number of Leydig cells (4), and (or) in the number of LH receptors per Leydig cell (5) could explain why the small LH pulses of the breeding season are able to trigger very large elevations in testosterone secretion. The LH-pulse pattern itself seems to be involved in maintaining testicular re¬ sponsiveness in that the elevation in testosterone secretion in response to an LH release is propor¬ tionately greater when LH releases are small and frequent (6).We hypothesized that establishing a high-fre¬ quency, low-amplitude pattern of LH pulses in rams would enhance the responsiveness of the testes to LH by increasing the number and (or) binding affinity of LH receptors. In a short-term study in the nonbreeding season, adult rams were given a series of LH injections to produce an LHpulse pattern resembling that of the breeding season. Changes in the pattern of testosterone se¬ cretion were assessed in relation to possible changes in gonadotropin receptors within the testis, as well as in FSH and PRL secretion which in rodent spe¬ cies also affect testosterone secretion (7,8).

show abstract

The Breeding Season and Ovulation Rate of DLS Ewes as Determined by Laparoscopy

Cited by 8 publications

References 3 publications

The effect of a light pulse and melatonin, alone or in combination, on the reproductive performance of Finn-cross ewes in spring in Israel

The effect of a light pulse and melatonin, alone or in combination, on the reproductive performance of Finn-cross ewes in spring in Israel

Duration of the seasonal anestrus in sheep selected for fertility in a fall-lambing system.

Enhanced testosterone secretion in adult rams after establishment of a high-frequency, low-amplitude pattern of LH pulses in the nonbreeding season occurs without changes in the number or binding affinity of testicular LH receptors

Contact Info

Product

Resources

About